Growing Concerns 549: Rhododendrons, care, girdling root

Early last summer I planted a rhododendron. It seemed to
do well where it was, near the house on the northwest side.
However, my dog just pulled it out of the ground! I was surprised
that the roots had not grown enough to anchor it. My soil is
heavily clay, although I had dug a large hole and mixed in some
peat moss to loosen it up.

Is it common for the roots to not grow much? What do I
do with it now? I was thinking I shouldn't put it back in the same
hole now that it's so cold, since apparently it didn't take too
well to the location. Should I just put it in a pot and keep it
cool until I can replant in spring?

J.

Dear J.,

A tree or shrub's roots should grow as much or more as its
branches each year. However, acid loving plants such as
rhododendrons tend to grow poorly in southeast Michigan's alkaline
soils. I've seen many with root balls the same size or smaller than
they had at the nursery, even after years on site.

So your shrub is on par with most rhododendrons in our area. You
can keep it in a pot in a cold garage and relocate it in spring.
But if it was growing foliage where you'd placed it and that spot
is sheltered from wind, you can put it back in the same hole.

Since you know what a tiny root ball it has you will know how
important it is to keep it watered during dry thaws. Mulch it two
to three inches deep with acidic materials such as pine needles,
cocoa hulls and coffee grounds. Once the shrub begins to grow new
leaves it will root into that acidic layer, so keep renewing the
mulch and don't plant any competing groundcover there.

Fertilize regularly from April through July with a water soluble
fertilizer for acid-loving plants. Sprinkle the solution on the
leaves as well as on the root zone, since both can absorb those
nutrients.

Dear Janet,

I had a Norway maple that died. After declining for
about two years it just didn't leaf out the third year. The tree
specialist said the cause was a girdling root. He said he knew
because the trunk was squareish. Is that truly a way to diagnose
that?

R.

Dear R.,

The Norway maple is famous for wrapping a root around and then
strangling itself as thickening root and expanding trunk run into
one another. Symptoms often appear as the tree reaches 15 to 20
years old -- growth slows, the center top of the tree may die back,
and yes, the side of the trunk that's being prevented from growing
becomes increasingly flat.

As Dan Kurkowski, Forester, explains it, "The total lack
of root flare is a definite 'telltale' of girdling roots. The trunk
will go right into the ground like a stovepipe."

Winter is a good time to take a look at your trees and see if
they have a healthy flare all the way around the base or are flat
on one or more sides. A girdling root that's caught early can be
cut away. You saw two years of decline before your tree died but
it's likely it was growing less well and showing trouble for ten
years or more, during which time that flattened side would have
been a flag to one who can read trees.

Green thumbs up

to being sure before you water that a plant has used all
excess moisture in its pot. Thirsty pots are lightweight or feel
dry on the surface. Since plants use water only if they have light
to photosynthesize, they use very little in these dark, short days
of winter. Overwatering, with attendant root rot, kills more plants
than underwatering!

Green thumbs down

to that every-year trampling of the same places under
trees and in foundation beds where you walk to put up and take down
holiday lights. Packing down the soil over plants' roots leads to
long term trouble like toppling and susceptibility to root
diseases. Take note this year of trampled ground and loosen there
with a garden fork in spring.